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<h2><b>ProFTPD module <code>mod_wrap</code></b></h2>
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<p>
This module is contained in the <code>contrib/mod_wrap.c</code> file for
ProFTPD 1.2.x, and is not compiled by default.  It enables the daemon to
use the common tcpwrappers access control library while in
<code>standalone</code> mode, and in a very configurable manner.

<p>
If not installed on your system, the TCP wrappers library, required by this
module, can be found
<a href="ftp://ftp.porcupine.org/pub/security/tcp_wrappers_7.6.tar.gz">here</a>,
on Wietse Venema's site.  Once installed, it <i>highly recommended</i>
that the <code>hosts_access(3)</code> and <code>hosts_access(5)</code> man
pages be read and understood.  The <a href="#Installation">installation</a>
of <code>mod_wrap</code> is fairly straightforward, with some caveats for
Solaris and FreeBSD users.

<p>
Many programs will automatically add entries in the common allow/deny files,
and use of this module will allow a ProFTPD daemon running in
<code>standalone</code> mode to adapt as these entries are added.  The
<code>portsentry</code> program does this, for example: when illegal access
is attempted, it will add hosts to the <code>/etc/hosts.deny</code> file.

<p>
The most current version of <code>mod_wrap</code> is distributed with the
ProFTPD source code.

<h2>Author</h2>
<p>
Please contact TJ Saunders &lt;tj <i>at</i> castaglia.org&gt; with any
questions, concerns, or suggestions regarding this module.

<h2>Thanks</h2>
<p>
<i>2000-05-29</i>: Thanks to David Douthitt &lt;ssrat <i>at</i> mailbag.com&gt;
for pointing out the usefulness of using <code>mod_wrap</code> in conjunction
with <code>portsentry</code>

<p>
<i>2001-03-01</i>: Updated the configuration directives, as per
lung <i>at</i> theuw.net's helpful suggestions.
   
<p>
<i>2001-09-24</i>: Thanks to Zenon Mousmoulas &lt;cajoline <i>at</i>
chaosengine.de &gt; for helping determine that adding <code>-lnsl</code> would
help in compiling <code>mod_wrap</code> with the stock RedHat
<code>libwrap.a</code>, so that recompiling tcpwrappers without NIS/YP support
should no longer be necessary.

<p>
<i>2001-09-27</i>: Thanks to Gabe Frost &lt;gfrost <i>at</i> gostnet.com&gt;
for helping track down several mergedown bugs.

<p>
<i>2001-12-19</i>: Thanks to Mark Castillo &lt;markc <i>at</i> webFreak.com&gt;
for pointing out the issue with passwords not being properly hidden

<h2>Directives</h2>
<ul>
  <li><a href="#TCPAccessFiles">TCPAccessFiles</a>
  <li><a href="#TCPAccessSyslogLevels">TCPAccessSyslogLevels</a>
  <li><a href="#TCPGroupAccessFiles">TCPGroupAccessFiles</a>
  <li><a href="#TCPServiceName">TCPServiceName</a>
  <li><a href="#TCPUserAccessFiles">TCPUserAccessFiles</a>
</ul>

<hr>
<h3><a name="TCPAccessFiles">TCPAccessFiles</a></h3>
<strong>Syntax:</strong> TCPAccessFiles <em>allow-filename deny-filename</em><br>
<strong>Default:</strong> None<br>
<strong>Context:</strong> server config, <code>&lt;VirtualHost</code>, <code>&lt;Global&gt;</code>, <code>&lt;Anonymous&gt;</code><br>
<strong>Module:</strong> mod_wrap<br>
<strong>Compatibility:</strong> 1.2.1 and later

<p>
TCPAccessFiles specifies two files, an allow and a deny file, each of which
contain the IP addresses, networks or name-based masks to be allowed or denied
connections to the server.  The files have the same format as the standard
tcpwrappers hosts.allow/deny files.

<p>
Both file names are required.  Also, the paths to both files must be the full
path, with two exceptions: if the path starts with <code>~/</code>, the check
of that path will be delayed until a user requests a connection, at which time
the path will be resolved to that user's home directory; or if the path starts
with <code>~user/</code>, where user is some system user.  In this latter case,
<code>mod_wrap</code> will attempt to resolve and verify the given user's home
directory on start-up.

<p>
The service name for which <code>mod_wrap</code> will look in the indicated
access files is <code>proftpd</code> by default; this can be configured via
the <code>TCPServiceName</code> directive.

<p>
There is a built-in precedence to the <code>TCPAccessFiles</code>,
<code>TCPGroupAccessFiles</code>, and <code>TCPUserAccessFiles</code>
directives, if all are used.  <code>mod_wrap</code> will look for applicable
<code>TCPUserAccessFiles</code> for the connecting user first.  If no applicable
<code>TCPUserAccessFiles</code> is found, <code>mod_wrap</code> will search for
<code>TCPGroupAccessFiles</code> which pertain to the connecting user.  If not
found, <code>mod_wrap</code> will then look for the server-wide
<code>TCPAccessFiles</code> directive.  This allows for access control to be
set on a per-server basis, and allow for per-user or per-group access control
to be handled without interfering with the server access rules.

<p>
Example:
<pre>
  # server-wide access files
  TCPAccessFiles /etc/ftpd.allow /etc/ftpd.deny

  # per-user access files, which are to be found in the user's home directory
  TCPAccessFiles ~/my.allow ~/my.deny
</pre>

<p>
See also:
 <a href="#TCPGroupAccessFiles">TCPGroupAccessFiles</a>,
 <a href="#TCPServiceName">TCPServiceName</a>,
 <a href="#TCPUserAccessFiles">TCPUserAccessFiles</a>

<p>
<hr>
<h3><a name="TCPAccessSyslogLevels">TCPAccessSyslogLevels</a></h3>
<strong>Syntax:</strong> TCPAccessSyslogLevels <em>allow-level deny-level</em><br>
<strong>Default:</strong> <code>TCPAccessSyslogLevels info warn</code><br>
<strong>Context:</strong> server config, <code>&lt;VirtualHost&gt;</code>, <code>&lt;Global&gt;</code>, <code>&lt;Anonymous&gt;</code><br>
<strong>Module:</strong> mod_wrap<br>
<strong>Compatibility:</strong> 1.2.1 and later

<p>
ProFTPD can log when a connection is allowed, or denied, as the result of rules
in the files specified in <code>TCPAccessFiles</code>, to the Unix
<code>syslog</code> mechanism.  A discussion on the <code>syslog</code> levels
which can be used is given in the <code>SyslogLevel</code> directive.

<p>
The <em>allow-level</em> parameter sets the syslog level at which allowed
connections are logged; the <em>deny-level</em> parameter sets the syslog
level for denied connections.

<p>
Example:
<pre>
  TCPAccessSyslogLevels debug warn
</pre>

<p>
<hr>
<h3><a name="#TCPGroupAccessFiles">TCPGroupAccessFiles</a></h3>
<strong>Syntax:</strong> TCPGroupAccessFiles <em>group-expression allow-filename deny-filename</em><br>
<strong>Default:</strong> <em>None</em><br>
<strong>Context:</strong> server config, <code>&lt;VirtualHost&gt;</code>, <code>&lt;Global&gt;</code><br>
<strong>Module:</strong> mod_wrap<br>
<strong>Compatibility:</strong> 1.2.1 and later

<p>
<code>TCPGroupAccessFiles</code> allows for access control files, the same
types of files required by <code>TCPAccessFiles</code>, to be applied to
select groups.  The given <em>group-expression</em> is a logical AND
expression, which means that the connecting user must be a member of all the
groups listed for this directive to apply.  Group names may be negated with a
<code>!</code> prefix.

<p>
The rules for the filename paths are the same as for
<code>TCPAccessFiles</code> settings.

<p>
Example:
<pre>
  # every member of group wheel must connect from restricted locations
  TCPGroupAccessFiles wheel /etc/ftpd-strict.allow /etc/ftpd-strict.deny

  # everyone else gets the standard access rules
  TCPGroupAccessFiles !wheel /etc/hosts.allow /etc/hosts.deny
</pre>

<p>
See Also: <a href="#TCPAccessFiles">TCPAccessFiles</a>

<p>
<hr>
<h3><a name="TCPServiceName">TCPServiceName</a></h3>
<strong>Syntax:</strong> TCPServiceName <em>name</em><br>
<strong>Default:</strong> <code>TCPServiceName proftpd</code><br>
<strong>Context:</strong> server config, <code>&lt;VirtualHost&gt;</code>, <code>&lt;Global&gt;</code><br>
<strong>Module:</strong> mod_wrap<br>
<strong>Compatibility:</strong> 1.2.1 and later

<p>
<code>TCPServiceName</code> is used to configure the name of the service under
which <code>mod_wrap</code> will check the allow/deny files.  By default, this
is the name of the program started, <em>i.e.</em> &quot;proftpd&quot;. However,
some administrators may want to use a different, more generic service name,
such as &quot;ftpd&quot;; use this directive for such needs.

<p>
<hr>
<h3><a name="TCPUserAccessFiles">TCPUserAccessFiles</a></h3>
<strong>Syntax:</strong> TCPUserAccessFiles <em>user-expression allow-filename deny-filename</em><br>
<strong>Default:</strong> <em>None</em><br>
<strong>Context:</strong> server config, <code>&lt;VirtualHost&gt;</code>, <code>&lt;Global&gt;</code><br>
<strong>Module:</strong> mod_wrap<br>
<strong>Compatibility:</strong> 1.2.1 and later

<p>
<code>TCPUserAccessFiles</code> allows for access control files, the same types
of files required by <code>TCPAccessFiles</code>, to be applied to select
users.  The given <em>user-expression</em> is a logical AND expression.
Listing multiple users in a user-expression does not make much sense; however,
this type of AND evaluation allows for expressions such as &quot;everyone
<i>except</i> this user&quot; with the use of the <code>!</code> negation
prefix.

<p>
The rules for the filename paths are the same as for
<code>TCPAccessFiles</code> settings.

<p>
Example:
<pre>
  # user admin might be allowed to connect from anywhere
  TCPUserAccessFiles admin /etc/ftpd-anywhere.allow /etc/ftpd-anywhere.deny

  # while every other user has to connect from LAN addresses
  TCPUserAccessFiles !admin /etc/ftpd-lan.allow /etc/ftpd-lan.deny
</pre>

<p>
See also: <a href="#TCPAccessFiles">TCPAccessFiles</a>

<p>
<hr>
<h2><a name="FAQ">FAQ</a></h2>

<p>
<font color=red>Question</font>: Using <code>mod_wrap</code>, connections
from hosts that have broken reverse DNS mappings are refused.  OpenSSH
uses the same <code>libwrap</code> library, and this doesn't happen.  Is it
a bug in <code>mod_wrap</code>?<br>
<font color=blue>Answer</font>:  No, it is not, strictly speaking, a bug
in <code>mod_wrap</code>.

<p>
Users who encounter this issue will usually find log messages that look
like the any/all of the following in their syslog:
<pre>
  proftpd: warning: can't verify hostname: gethostbyname(<i>dns-name</i>) failed
  proftpd: warning: can't verify hostname: getaddrinfo(anothername.net, AF_INET) failed
  proftpd: warning: host name/name mismatch: somedomain.com != vs-23.somename.com
</pre>
These log messages do <b>not</b>, in fact, come from <code>proftpd</code>.
Instead, they come from the <code>libwrap</code> library, which is used by
the <code>mod_wrap</code> module.  In particular, the <code>libwrap</code>
library emits these log messages when it has been compiled with the
<code>-DPARANOID</code> compile-time option (and most installations of the
<code>libwrap</code> library are compiled this way).

<p>
OpenSSH allows such connections because the OpenSSH code, when using the
<code>libwrap</code> library, does not check for paranoid/unknown results
from the <code>host_access()</code> function of the <code>libwrap</code>
library.  The <code>mod_wrap</code> module for ProFTPD <i>does</i> check
for these values, thus why those connections are refused by
<code>mod_wrap</code> but not OpenSSH.  This just demonstrates that not all
applications use the <code>libwrap</code> library the same way.

<p>
The solution, in most cases, is to switch to using the newer
<a href="mod_wrap2.html"><code>mod_wrap2</code></a> module, which does
<b>not</b> use the <code>libwrap</code> library (and thus does not encounter
this issue).

<p>
<hr>
<h2><a name="Installation">Installation</a></h2>
Use of <code>mod_wrap</code> is straightforward, with some minor caveats.  If
you're using Solaris, you'll need to obtain and build the tcpwrappers library,
as this library does not come installed on stock Solaris systems.  If you're
using FreeBSD or Mac OSX (and possibly other versions), you'll need to change
the following line in the header of <code>mod_wrap.c</code>:
<pre>
 * $Libraries: -lwrap -lnsl$
</pre>
to be:
<pre>
 * $Libraries: -lwrap$
</pre>
This line is needed on Linux and Solaris machines, to properly link against
the <code>libnsl.a</code> library, which implements the NIS/YP functions.
In FreeBSD and Mac OSX, these functions are implemented in <code>libc</code>.

<p>
Then, you need simply follow the normal steps for using third-party modules in
ProFTPD:
<pre>
  $ ./configure --with-modules=mod_wrap
  $ make
  $ make install
</pre>

<p>
<hr>
<font size=2><b><i>
&copy; Copyright 2000-2009 TJ Saunders<br>
 All Rights Reserved<br>
</i></b></font>
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